Hydrogen generation by OTEC electrolysis, and economical energy transfer to world markets via ammonia and methanol

Abstract

OTEC plantships sited in tropical oceans would generate 150–400 MWe (net) of low-cost electric power per plantship. These plantships would tap a virtually unlimited source of energy for economical production of hydrogen by water electrolysis. Hydrogen could be delivered to U.S. users from such plantships via hydrogen liquefaction, transport and storage, or by incorporation in a chemical carrier and shipment by conventional transport methods. Costs of OTEC energy in the form of liquid fuels delivered to U.S. users are estimated to be favorable compared with equivalents derived from land-based sources after 1990. The paper briefly reviews the status of OTEC technology and projected costs for plantship construction and deployment. This provides a basis for a more detailed description of the onboard processes and costs for production of hydrogen, ammonia and methanol on OTEC plantships. Estimated costs for the three fuels delivered to U.S. ports are: liquid hydrogen $41–66 MBtu, ammonia $10–16 MBtu −1, methanol $9–14 MBtu −1 (1983$). Production of OTEC methanol involves transport of coal to the plantship where it is oxidized to carbon monoxide with oxygen and steam followed by reaction of the gas mixture with added electrolytic hydrogen. The process efficiently uses both the hydrogen and the oxygen produced by onboard electrolysis of water.